Presentation, diagnosis and management of bowel
obstruction
Mr Alastair Moses
Consultant Surgeon
NHS Tayside
Pathophysiology
• Any part of the GI tract may become obstructed and present as an acute abdomen.
• Dilatation of bowel proximal to obstruction with air and fluid.
• Peristalsis is disrupted.
• The manner of presentation depends on the level of obstruction.
Pathophysiology: level of obstruction
• Upper small bowel obstruction:
Can present acutely within hours of onset with large volumes of gastric, pancreatic and biliary secretions regurgitated into the stomach and vomited.
Pathophysiology: level of obstruction
• Distal small bowel / large bowel obstruction:
Can present with colicky abdominal pain and
distension. Vomiting (possibly ‘faeculent’)
can occur subsequently.
Symptoms of intestinal obstruction
• Vomiting
• Pain
• Constipation
• Large bowel obstruction
• Incomplete obstruction
Symptoms of intestinal obstruction: vomiting
• The more proximal the obstruction, the earlier vomiting develops.
• Can occur even if nothing is taken by mouth: GI secretions continue to be produced –
Saliva, gastric , pancreatic, bile, small intestine (up to several litres per day).
Symptoms of intestinal obstruction: vomiting
• Nature of vomitus gives clues to the level of obstruction:
- Semi-digested food eaten a day or two previously (no bile) suggests gastric outlet obstruction.
- Copious bile-stained fluid suggests upper small bowel obstruction.
Symptoms of intestinal obstruction: vomiting
• Nature of vomitus gives clues to the level of obstruction:
- Thicker, brown, foul-smelling vomitus (‘faeculent’) suggests a more distal obstruction.
[Faeculent vomitus contains altered small bowel contents, not faeces].
Symptoms of intestinal obstruction: pain
• Distension of the bowel caused by swallowed air and intestinal fluid secreted proximal to an obstruction causes pain.
• Intermittent episodes of colicky pain occur as peristalsis attempts to overcome the obstruction.
Symptoms of intestinal obstruction: constipation
• Propulsion of bowel contents is arrested.
• Bowel gas is absorbed distal to the obstruction.
• ‘Absolute constipation’ (neither faeces or flatus passed rectally) is pathognomonic of bowel obstruction.
Symptoms of intestinal obstruction: large bowel obstruction
• Symptoms tend to develop more gradually in large bowel obstruction due to the large capacity of the colon and caecum and their absorptive activity.
Symptoms of intestinal obstruction: large bowel obstruction
• If the ileo-caecal valve remains competent (50% cases) backward flow of accumulated bowel contents is prevented .
• The thin walled caecum progressively distends with swallowed air and eventually may rupture: ‘closed loop obstruction’.
Symptoms of intestinal obstruction: large bowel obstruction
• If the ileo-caecal valve becomes incompetent (50% cases) the small bowel distends, delaying the onset of symptoms.
Symptoms of intestinal obstruction: incomplete obstruction
• If the bowel is only partially obstructed, the clinical features may be less clearly defined.
• Vomiting may be intermittent and bowel habit erratic.
Symptoms of intestinal obstruction: incomplete obstruction
• Chronic incomplete obstruction leads to gradual hypertrophy of the muscle of the bowel wall proximally.
• Peristaltic activity in this hypertrophic muscle is responsible for bouts of colicky pain which can be more prominent than in complete obstruction.
Physical signs of intestinal obstruction
• Dehydration (dry mouth, loss of skin turgor and elasticity)
• Abdominal distension
• Visible peristalsis
• Relative lack of abdominal tenderness (obstruction with tenderness may indicate bowel strangulation)
Physical signs of intestinal obstruction
• Obstructing abdominal mass may be palpable
• On percussion the centre of the abdomen tends to be resonant due to gaseous distension
• Groins must be examined for an obstructing hernia
Physical signs of intestinal obstruction
• Bowel sounds are traditionally described as high-pitched and tinkling. In practice they may be absent at the time of auscultation, echoing (cavernous quality), or may sound like water lapping against a boat.
Investigation of suspected bowel obstruction
• Most useful initial investigation is a supine abdominal X-ray:
• Bowel proximal to the obstruction is distended with gas.
• Erect abdominal films are no longer part of routine clinical practice (multiple air fluid levels).
Investigation of suspected bowel obstruction
• Distended small bowel loops tend to lie in a central position and have valvulae coniventes.
• Distended large bowel tends to lie in its anatomical position and has haustra coli.
Investigation of suspected bowel obstruction
• Initial plain abdominal X-ray is often followed by CT scan of abdomen to look for the cause of obstruction.
• A ‘cut off’ will be observed between dilated proximal and collapsed distal bowel at the site of obstruction.
Principles of management of intestinal obstruction
• Initial management is ‘drip and suck’.
• Nil by mouth.
• Insert IV cannula and send blood for: urea & electrolytes.
• Resuscitate with IV fluids, replacing electrolyte losses.
• Pass a nasogastric tube to decompress the stomach.
Mechanical causes of bowel obstruction
• Adhesions or bands: congenital or resulting from previous abdominal surgery or peritonitis.
Mechanical causes of bowel obstruction
• Incarcerated external hernias:
1. Inguinal2. Femoral3. Umbilical4. Paraumbilical5. Ventral6. incisional.
• Internal hernias.
Mechanical causes of bowel obstruction
• Volvulus of large or small bowel:
A mobile loop of bowel rotates causing
obstruction at its neck.
Mechanical causes of bowel obstruction
• Tumours
1. Gastric cancer blocking the pylorus
2. Small bowel tumours (rare)
3. Large bowel cancer
Mechanical causes of bowel obstruction
• Inflammatory strictures:
1. Crohn’s disease
2. Diverticular disease
These obstructions are usually incomplete.
Mechanical causes of bowel obstruction
• Bolus obstruction:
1. Food bolus
2. Impacted faeces
3. Impacted ‘gallstone ileus’ (rare)
4. Trichobezoar (rare)
Mechanical causes of bowel obstruction
• Intussusception: a segment of bowel wall becomes telescoped into the segment distal to it.
• Usually initiated by a mass in the bowel wall: enlargement of lymphatic tissue or tumour.
• Common in children.
Bowel strangulation
• Strangulation occurs when a segment of bowel becomes trapped so that its lumen becomes obstructed (incarcerated) and its blood supply compromised (strangulated).
• If strangulation is not relieved this will progress to infarction and perforation.
Bowel strangulation
• Pain over a hernia suggests possible strangulation and is a sign requiring urgent surgical intervention.
• Can occur in external hernia or volvulus.
Adynamic bowel obstruction
• Paralytic ileus
• Pseudo-obstruction